1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to performing measurements in a carrier aggregation scenario.
2. Introduction
A wireless communication network may be deployed over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, access points (e.g., corresponding to different cells) are distributed throughout a network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the network.
Some of these access terminals may support the concurrent use of multiple carriers. For example, in a carrier aggregation scenario, an access point may allocate several carriers for communication between the access point and an access terminal. Here, the number of carriers allocated may be based on the number of carriers that the access terminal may concurrently support and the traffic load of the access terminal.
An access terminal may support multiple carriers through the use of one or more receivers (e.g., receiver front-ends). For example, the available radiofrequency (RF) spectrum for a network may be divided into a set of bands (each of which has a corresponding bandwidth). These bands may or may not be contiguous within the RF spectrum. Several carriers are defined within each band, whereby a given carrier corresponds to a nominal carrier frequency and associated bandwidth. In the event contiguous carriers are allocated to an access terminal, the access terminal may be able to use a single receiver to receive data on these carriers (e.g., by tuning the receiver to acquire data over the collective bandwidth of these carriers). Conversely, if non-contiguous carriers (e.g., carriers in different bands) are allocated to an access terminal, the access terminal may need to use multiple receivers to receive data on these carriers.
In general, at a given point in time, an access terminal will be served by a given access point in the network. As the access terminal roams throughout this geographical area, the access terminal may move away from its serving access point and move closer to another access point. In addition, signal conditions within a given cell may change, whereby an access terminal may be better served by another access point. In these cases, to maintain mobility for the access terminal, the access terminal may be handed-over from its serving access point to the other access point.
To facilitate such access terminal mobility, an access terminal conducts searches for signals from nearby access points in an attempt to ensure, for example, that the “best” handover candidate may be readily identified when signal conditions at the current cell deteriorate. For example, an access terminal may regularly monitor for (i.e., measure) pilot signals from nearby access points to identify potential target access points to which the access terminal may be handed-over. In some cases, these access points may operate on a different carrier than the current serving access point. Thus, this measurement may involve measuring on different carriers (i.e., inter-frequency measurements). Conducting a measurement on one carrier may, however, impact the ability to receive on another carrier.
Conventionally, measurement gaps are employed for inter-frequency measurements whereby transmissions from an access point to an access terminal on one carrier are temporarily stopped while the access terminal conducts a pilot measurement on another carrier. However, the use of these measurements gaps may negatively impact throughput on the non-measured carrier. Thus, there is a need for effective techniques for conducting inter-carrier measurements.